usb screen: Stop scrolling the entire display.

It's not easy for the originating screen to perform cleanup in case of USB
because the usb screen is invoked indirectly via default_event_handler(). To
avoid stale scrolling lines perform the cleanup in the usb screen itself.

Side effect should be no worse than scrolling lines to restart in SBSes that
show during USB.

Change-Id: I9aa491b3d4b649c0b3be70048ebcb9d817c0356c

1 files changed, 5 insertions, 1 deletions

diff --git a/apps/gui/usb_screen.c b/apps/gui/usb_screen.c
index 569e694870..20af4dc3da 100644
--- a/apps/gui/usb_screen.c
+++ b/apps/gui/usb_screen.c
@@ -264,8 +264,12 @@ void gui_usb_screen_run(bool early_usb)
     FOR_NB_SCREENS(i)
     {
         struct screen *screen = &screens[i];
-
+        /* we might be coming from anywhere, and the originating screen
+         * can't be practically expected to cleanup the UI because
+         * we're invoked via default_event_handler(), therefore we make a
+         * generic cleanup here */
         screen->set_viewport(NULL);
+        screen->scroll_stop();
 #ifdef HAVE_LCD_CHARCELLS
         /* Quick fix. Viewports should really be enabled proper for charcell */
         viewport_set_defaults(&usb_screen_vps_ar[i].parent, i);